Milky Way Behaving Badly

Head over to Space.comfor a story about the dark side of our well behaved galaxy's nature, its being throwing its weight around and generally being a bad neighbour. The story is all about the streams of stars that are being found trailing around the Milky Way, these trails are thought to be the shredded remains of dwarf galaxies or globular clusters that wandered too close to the MW. Below you can see some of the streams uncovered by the Sloan Digital Sky Survey. The streams are detected by looking at the colours and positions of a huge number of stars over as large an area as possible, doing this it is possible to pick out groups of stars with the same sort of colour, implying that they probably formed at the same time from the same material.


Some of the streams have been associated with known GCs or dwarf galaxies, basically these objects lie right in the middle of the stream, in the pictorial representation at the top you can see the original dwarf with its tails of stars which spread out both in front and behind it in its orbit of the MW. Over time the streams will stretch further and further, getting progressively thinner and more tangled, until they form a diffuse halo of stars around the MW.

This kind of research is interesting because the current theories for the formation of galaxies predict that there should be many more dwarf galaxies around the MW than we see at present, one solution is that many of them have simply been torn apart by the MW and their stars spread into the halo of the galaxy. If enough of these streams are found this could help solve this so called "missing satellite problem".